The 2009 passage of the Family Smoking Prevention and Tobacco Control Act (FSPTCA) gave the Food and Drug Administration (FDA) the authority to reduce levels of nicotine in cigarettes if appropriate for public health. This project addresses an area targeted for study by NIH and the FDA to assess the impact of products with reduced toxicity on tobacco use behaviors. Very-low nicotine content cigarettes (VLNCC) have been shown in some studies with smokers from the general population to reduce craving and withdrawal for tobacco relative to abstinence with little or no compensatory smoking, suggesting that a mandated reduction in the nicotine yield of cigarettes could substantially reduce smoking rates. This may be a particularly effective method of reducing smoking and smoking-related disease in special populations that have very high rates of tobacco dependence, such as people with substance use disorders (SUD). However, the consequences of this policy for smokers with SUD have not been investigated, and a call has gone out for studies of the safety of these products with vulnerable populations such as these. The purpose of this study is to determine the efficacy, acceptability and unintended consequences of VLNCC in smokers with SUD (current or past year). The primary aims are to determine whether VLNCC will increase smoking cessation and reduce cigarette use, cotinine, and biomarkers of toxicity in smokers with SUD relative to baseline and to those randomized to a normal nicotine content cigarette (NNCC), and to determine any unintended effects of VLNCC on substance use and cravings to use substances so as to investigate safety. Secondary aims are to study effects on cigarette craving and nicotine withdrawal and dependence (mechanisms), and state depression (safety). A 2-group between-group by pre-post design will compare 6 weeks of VLNCC to NNCC; all smokers will also be provided with smoking counseling. Follow-up over 6 months will assess effects after return to usual cigarettes. The importance is in determining the viability and safety of this publi health strategy in terms of effects on both smoking and other substance use in a highly addicted population, which is essential to determine before the FDA implements this policy.